David,
FYI, the Linbox bug you and Gabe found has been fixed in svn Linbox,
so it will be fixed in SAGE in the not-too-distant future.
Thanks Pascal!!
-- william
---------- Forwarded message ----------
From: Pascal Giorgi <[EMAIL PROTECTED]>
Date: Aug 8, 2007 9:00 AM
Subject: [linbox-devel] Re: linbox det bug
To: linbox-devel <[EMAIL PROTECTED]>
Hi William,
I looked for your bug and I finally managed to fix it.
It came from an optimization code for applying an integer dense matrix
to a vector,
which is, unfortunately, used in integer determinant computations.
It is now updated in the svn repository.
Pascal.
On Aug 3, 1:27 am, "William Stein" <[EMAIL PROTECTED]> wrote:
> Hi Clement,
>
> Any chance you could look into this. It's an 8x8 full matrix where
> linbox (via SAGE)
> computes the wrong determinant?
>
> Here's the SAGE session that gives the bad result:
>
> sage: M = matrix(
> [
> [-3821257660, -3821257669, -1736935303, -2779096486, -1736935306,
> -2779096486, -2779096489, -2779096483],
> [-3821257669, -3821257660, -1736935303, -2779096486, -1736935303,
> -2779096489, -2779096486, -2779096489],
> [-1736935303, -1736935303, -789516040, -1263225676, -789516049,
> -1263225676, -1263225679, -1263225676],
> [-2779096486, -2779096486, -1263225676, -2021161072, -1263225676,
> -2021161081, -2021161081, -2021161084],
> [-1736935306, -1736935303, -789516049, -1263225676, -789516040,
> -1263225676, -1263225676, -1263225676],
> [-2779096486, -2779096489, -1263225676, -2021161081, -1263225676,
> -2021161072, -2021161081, -2021161081],
> [-2779096489, -2779096486, -1263225679, -2021161081, -1263225676,
> -2021161081, -2021161072, -2021161081],
> [-2779096483, -2779096489, -1263225676, -2021161084, -1263225676,
> -2021161081, -2021161081,-2021161072] ])
> sage: M._det_linbox()
> ERROR in reconstruction ?
> 0
>
> The C++ code against linbox that's used for _det_linbox is:
>
> void linbox_integer_dense_det(mpz_t ans, mpz_t** matrix, size_t nrows,
> size_t ncols) {
> commentator.setMaxDetailLevel(0);
> commentator.setMaxDepth (0);
>
> DenseMatrix<Integers> A(new_matrix_integers(matrix, nrows, ncols));
> GMP_Integers::Element d;
> det(d, A);
> mpz_set(ans, spy.get_mpz(d));
>
> }
>
> Thoughts?
>
> --
> William Stein
> Associate Professor of Mathematics
> University of Washingtonhttp://www.williamstein.org
--
William Stein
Associate Professor of Mathematics
University of Washington
http://www.williamstein.org
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